DRIVES & MOTORS


INVESTIGATING THE SCAL SAVINGS FROM DRIVES IN C


Torben Poulsen, business development manager at


ABB Drive Products, discusses how new research has quantified the energy efficiency potential of variable speed drives (VSDs) in applications with constant output. The findings suggest that nearly 20 terawatt-hours (TWh) of annual energy savings for the European Union could be unlocked…


V


SDs are well-regarded for their ability to reduce energy consumption in variable flow


applications, such as pumps and fans, where they typically offer energy savings of 30% or more. But there is still a reluctance among operators to implement drives in constant load applications, often due to concerns about potential inefficiency. Constant load systems operate at a set output,


like a water pump continuously running at a set rate of delivery. By comparison, variable flow systems adjust their output to real-time demand, such as a fan increasing or reducing speed in response to occupancy. To determine the suitability of VSDs in constant


load applications, the Fraunhofer Institute for Chemical Technology (ICT), under commission from the European Committee of Manufacturers of Electrical Machines and Power Electronics (CEMEP), conducted independent research on the subject. The results are notable: fans and pumps operating with a constant load show energy savings of up to 12% per installation when fitted with VSDs. In the EU alone, this equates to a potential annual energy saving of 19.6 TWh, which is over 4% of the region’s annual electric motor power consumption.


Fraunhofer’s study indicates that drives


in constant load pumps could save around 15.7 TWh/year alone, while in fans they could contribute an additional 3.9 TWh/year saved. These reductions would prevent approximately


38 million tons of CO2 emissions total each year, based on Europe’s current energy mix. This represents a giant leap towards meeting the EU’s 2040 carbon neutrality targets.


HOW VSDS IMPACT EFFICIENCY IN CONSTANT LOAD APPLICATIONS Although some processes appear stable when viewed as a whole, the equipment supporting them – such as pumps used in water treatment or for pressure boosting – often operates far from its optimal efficiency point. Pumps and fans are routinely oversized to account for potential future needs, design uncertainties, or worst-case scenarios. The resulting energy waste is entirely avoidable. Conventional measures to moderate flow in


over-specified systems include the practice of mechanical throttling, with devices such as valves or dampers ‘applying the brakes’. While this limits


the flow at the output, it has no real impact on the amount of energy consumed by the motor itself. Consequently, the motor continues to run at a higher power than needed, even when the system only requires a fraction of its total capacity. VSDs do incur a slight energy loss, as their


efficiency typically ranges from 95 to 99%. However, installing a VSD eliminates the frictional and pressure losses that come with traditional throttling methods. Additionally, downsized equipment with smarter control will better match the actual needs of the application.


SYSTEMIC OVERSIZING REMAINS PREVALENT The study indicates that about half of pump systems and 40% of fan systems in the EU operate under constant load conditions. This category includes 56% of drinking water pumps, 91% of wastewater pumps that move liquids, and 98% of those that pump solids. HVAC fans show similar characteristics, with about 70% classified as constant load systems. Such systems are rarely optimised. They operate


under a wide range of load conditions, involving periods of full, partial, or overload. The study shows that efficiency losses can approach around 5% during partial load, and up to 1.5% during overload. These are losses that VSDs could eliminate.


The study indicates that about half of pump systems and 40% of fan systems in the EU operate under constant load conditions


16 ENERGY & SUSTAINABILITY SOLUTIONS - Autumn 2025


RETHINKING SYSTEM SIZING AND FIT Integrating VSDs into constant load applications will require a shift in operators’ approaches to system design. Conservative equipment sizing often results in systems that run outside of their Best Efficiency Point (BEP). While this has historically been accepted as an unavoidable compromise, VSDs can address this issue by enabling ongoing adjustment as conditions


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